These type of signs consist of a sign tray normally 3mm aluminium which in this case looks to me mounted on to a wooden frame sometimes it will be mounted to aluminium angle, then it as an illuminated sign case mounted to it. Regards to responsibility i state on install invoices that yearly maintenance and inspection is required as any product that is installed outside in all weather conditions. Unfortunately some of the wood that can be seen in the picture could be as old as the building (Circa 1920-30s) and would have originally been part of the original shop sign which was built as part of the building and meant that it was totally integrated into the building including being water tight. Now the problem occurs when they rip these old signs off just leaving the structural timbers behind. In an ideal world they should close off the opening with structural ply board, water proof & then fit the signage, this isn't always done due to bad ethic's or financial constraints etc. Problems then occur when water starts to leak behind the sign tray causing the previously very dry untreated wood to soak up water like a sponge eventually rotting. As regards to permits etc most signage in the UK doesn't require any we do have building control and planning but if a building has had a sign previously then they don't normally get involved.
Its only just happened here so not many facts at the moment apart from it being a very young man if anything further comes up will try to post an update
Kev